What is BSS84 MOSFET : Pin Configuration & Its Working

The development of p-channel enhancement mode transistor-like BSS84 MOSFET is developed by ON Semiconductor Corporation with DMOS technology & high cell density. This development process is extremely high which reduces on−state resistance & also provides fast switching, reliable & rugged performance.

This transistor is used with less effort in most of the applications which require up to 0.13 A of DC & can generate a current equal to 0.52 A. This transistor is especially used in low voltage-based applications. This article discusses an overview of BSS84 MOSFET, pin configuration, working, and its applications.

What is BSS84 MOSFET?

BSS84 is one kind of Metal Oxide Semiconductor Field Effect Transistor (MOSFET) with P-channel enhancement mode. It is mainly designed to use in different applications like a switch device with high speed, computing, consumer, industrial & communication applications.


This is a Diffusion MOS (Metal-Oxide-Semiconductor) transistor that is appropriate for applications that use high frequency because of the quick switching characteristics. This kind of MOSFET is mainly designed for reducing state resistance and also to maintain better switching performance so that it is perfect for power management with high-efficiency applications.

Pin Configuration

BSS84 MOSFET is a three-terminal transistor where each pin and its functionality are discussed below. The pin diagram of BSS84 MOSFET is shown below.

BSS84 MOSFET Pin Configuration
BSS84 MOSFET Pin Configuration

Pin1 (Drain): The flow of current in this transistor will be throughout the source pin & it goes out using the Drain pin.

Pin2 (Gate): The activation & deactivation of this transistor can be done based on the applied voltage at the gate pin.

Pin3 (Source): The source pin is used to supply to the transistor.

Features & Specifications

The features and specifications of BSS84 MOSFET include the following.

  • This is a P-Channel & enhancement mode MOSFET
  • Operating temperature ranges from-55ºC to +150ºC
  • The threshold voltage is low
  • Dissipation of power max is 0.30W
  • High-speed switching
  • Allowed pulsated Drain current is -1.2A
  • Turn ON resistance is extremely low
  • Continuous drain current max is -130mA
  • No inferior breakdown
  • Gate-Source voltage max is ±20V
  • Interfacing can be done directly to TTL & CMOS
  •  Drain-Source voltage max is -50V
  • Small signal p-channel switch controlled by voltage
  • Cell design is high density for Low RDS(on)
  • The Saturation current is high
  • Pb free & Halogen-free device
  • Appropriate to use through all logic families with 5V
  • Appropriate for fewer gate drive sources
  • The threshold voltage is low
  • Switching speed is high
  • Gate (G) to source (S) voltage is ±20V
  • The polarity of the transistor is P-Channel
  • The breakdown voltage of drain to source is- 50 V
  • The breakdown voltage of the gate to the source is +/- 20 V
  • The nonstop drain current is 0.13 A
  • Single configuration
  • Drain to Source resistance like RDS (on) is10 Ohms
  • Reel packaging
  • Operating Temperature max is + 150 C
  • Case or package is SOT-23
  • The style of mounting is SMD or SMT
  • Low Input Capacitance
  • Switching speed is fast
  • Leakage of Input or Output is low

Equivalent BSS84 MOSFETs are ZXMP2120FF, NDS332P, AO3401 & IRLML6402

BSS84 MOSFET is used as a high-speed switching device to replace all usual transistors which are used in digital circuits because it is particularly designed through the high cell density method for switching applications with high speed.

This transistor is exclusively designed to use in applications that use low voltage. So this device is mainly chosen within the systems which operate through a battery.

The designing of this can be done through a special design procedure leading to extremely less turn ON resistance throughout the operation. So in some of the applications, this resistance characteristic is a condition. Therefore this transistor is used in high-efficiency applications.

How to use BSS84 MOSFET/Circuit Diagram?

The simple application circuit of BSS84 MOSFET is shown below. Here this MOSFET is mainly used like a switching device where the motor used in the circuit works as a load.

BSS84 MOSFETCircuit Diagram
BSS84 MOSFETCircuit Diagram

The MOSFET’s gate terminal is switched from a voltage signal like ‘Vo’. Here this voltage signal is the output of a microprocessor/ microcontroller.

The power supply given to the MOSFET is received from a negative source of power like VDS = -10V. We know that the P-channel enhancement MOSFET characteristics,

This transistor does not perform once the voltage supply at the junction of G (gate) to S (source) does not go under a fixed threshold voltage.

The flow of current throughout Drain (D) can be decided through the voltage on the G (gate) terminal equal to a fixed point.

Thus, when the gate voltage is low, the conduction resistance of MOSFET is low & the drain current is high. This kind of MOSFET performs simply once a negative voltage is there at the gate (G) terminal, consequently, the gate voltage is removed directly then the MOSFET will stop working.

So the same characteristic is applied to this application circuit for understanding. Let us consider the voltage signal like ‘Vo’ is not given to the gate terminal of the transistor. So under this condition, the transistor will not perform as a least negative -2V voltage need to be there at the gate terminal for activating the device.

When the -5V gate signal is given through the microcontroller at a set time, then MOSFET will start performing. Thus now current supplies throughout the transistor & this current flow can lead to a drop in voltage beyond load. So this voltage drop will switch ON the load.

The load used in the circuit is the motor which will rotate continuously until the microcontrollers negative voltage is there & the direct voltage like ‘Vo’ will go to 0V to stop the motor from rotating.
Thus, BSS84 is used as a switching device in the above application & in a similar method, we can utilize the transistor in other different circuits.

Where to use BSS84 MOSFET/Applications

The applications of BSS84 MOSFET include the following.

  • Power Management
  • Industrial, Communications
  • Networking
  • Computers
  • Computer Peripherals
  • Consumer Electronics
  • Systems operated through battery
  • Switching applications
  • Lighting systems
  • Signal Amplifiers
  • Functions of Power management
  • Line current interrupter within telephone sets
  • Liner transformer drivers
  • Load Switching
  • Protection of battery
  • DC/DC converter
  • Controlling of Power management
  • Controlling of DC motor

Thus, this is all about an overview of the BSS84 MOSFET datasheet which includes its pin configuration, specifications, features, circuit, and applications. The main benefits of a BSS84 MOSFET mainly include, saturation current is high, DMOS technology, switching is superior, high density-based cell design, small-signal p-channel switch controlled by voltage, performance is reliable and rugged. Here is a question for you, what are the disadvantages of MOSFET?